Conventionally, vibration rollers used for repairing paved roads and others have a emergency stop device for preventing the operator from being caught between the roller and an unnoticed obstacle behind him when the roller moves backward. The emergency stop device stops reverse travel of the roller by switching a travel lever on an operating portion of the rear of the roller to a neutral position when the operator hits the obstacle and touches a safety switch sticked out of the operating portion.
In the conventional emergency-stop-device, when the operator hits the obstacle and the safety switch is activated while the roller moves backward, the travel lever on the operating portion is displaced to the neutral position and the travel switching device of the roller is switched to a neutral position, therefore, the reverse travel of the roller is stopped automatically. Accordingly, this kind of conventional emergency-stop-device is considered to theoretically ensure safety of the operator.
However, in fact, although the safety switch is turned on, when the operator hits the obstacle and the emergency stop device is activated, so that the travel lever on the operating portion may be switched from a reverse position to the neutral position, the roller does not stop and an accident in which the operator is seriously injured by being caught between the obstacle and the roller happens.
The reason of that, according to research, is turned out as follows. The reason is that the operator holds the travel lever in the reverse position while the roller moves backward, therefore, when he hits the obstacle behind him, he keeps tightly the travel lever in the reverse position in shock without releasing it. Accordingly, the roller does not stop and keeps on moving backward although the emergency stop device is activated and intends to switch the travel lever on the operating portion from the reverse position to the neutral position.
As means for solving this problem, the mechanics of the emergency stop device stopping the roller is advocated in the related art (for example, Japanese Patent Application KO-HYO Publication No. 2002-501135). The emergency stop device in the related art stops the roller moving backward; when the operator hits the obstacle behind him, the safety switch is activated, and the travel switching device of the roller is switched automatically to the neutral position; although the operator holds tightly the travel lever in the reverse position in shock.
In the emergency stop device, when the operator hits the obstacle behind him while the roller moves backward, a conical top of the safety switch is pressed into between a travel lever coupled like a clutch and an adjusting element, and separates the travel lever and the adjusting element. Therefore, even if the travel lever is placed in the reverse position, the adjusting element is pulled to the neutral position regardless of the position of the travel lever, thus, the roller stops automatically.
The emergency stop device has a mechanism in which a conical top like a pencil of the safety switch is disposed in back of a narrow gap between the travel lever coupled like a clutch and the adjusting element, the switch is activated after the conical top of the safety switch is pulled into between the travel lever and the adjusting element, and the switch separates them. Therefore, the emergency stop device has problems. The problems are that, if the conical top of the safety switch is not disposed with a proper height and a proper angle for the gap between the travel lever and the adjusting element, the emergency stop device does not work properly because the conical top of the safety switch pulled into between the travel lever and the adjusting element cannot separate them properly, and the travel lever is held in the reverse position continuously.